Simplify coalesce expressions

[Praveen2112]

For coalesce expression like coalesce(colA, colA) can be simplified to colA and for expressions like coalesce('1', colA) can be simplified to '1'. This patch captures those pattern and simplifies them. Also updated the test for the above changes

[Praveen2112]

@kokosing Have added support for nested coalesce expressions.

[kokosing]

@sopel39 Would you like to take a look also?

[sopel39]

what if there are more levels of recursion? Make it recursive

[Praveen2112]

But the current model is recursive right. We have added tests with more levels of coalesce and it passed it.

[sopel39]

It only supports one level of recursion.

[Praveen2112]

Won't ExpressionInterpreter#processWithExceptionHandling will call other levels ? We just need to check if one of argument is of CoalesceExpression If yes we will extract its arguments and push it to the outer expression and processWithExceptionHandling will ideally handle at more levels

If I am not wrong recursive implementation will simplify
coalesce(coalesce(unbound_long, coalesce(unbound_long, 1)), unbound_long2) to coalesce(unbound_long, 1)

[sopel39]

Right, thanks

[Praveen2112]

Sorry I have replaced it with isDeterministic((CoalesceExpression) expression)

[sopel39]

I mean I think that isDeterministic((CoalesceExpression) expression) can be removed completely. We don't need to check if nested coalesce is deterministic

[Praveen2112]

But in that case it will simplify coalesce(unbound_long, coalesce(random(), 1) to coalesce(unbound_long, random(), 1).

[Praveen2112]

@sopel39 Removed the deterministic check as it is not required now

[sopel39]

Thank you. Ping us when release is done to land it

[findepi]

@Praveen2112 this will help a bit with #12155 (as per #12155 (comment)). Nice

[Praveen2112]

@findepi I guess this one #12193 would also help the above issue.

[sopel39]

Right, thanks

[highker]

Merged